1. Field of the Invention
The present invention relates to a controller and a control method for a refrigerating system.
2. Description of the Related Art
JP-A-2004-257666 discloses a technique of a refrigerating system having plural showcases, plural refrigerating machines and control units for controlling the plural showcases and the refrigerating machines. In this refrigerating system, when a defrost operation of removing frost adhering to a heat exchanger of a showcase to be defrosted is executed, under the control of each control unit provided to a defrost target showcase (or the same type (i.e., low-temperature type or high-temperature type) of defrost target showcases), circulation of refrigerant through the defrost target showcase is stopped to increase the temperature of the heat exchanger and thus defrost the heat exchanger concerned, and then the inside temperature of the defrost target showcase is cooled to a set temperature. Accordingly, when the defrost operation as described above is executed under the control of the individual control unit provided to the defrost target showcase, the circulation amount of refrigerant flowing through the refrigerant circuit of the refrigerating system rapidly varies and thus the load imposed on the refrigerating machines rapidly varies, so that the operation efficiency of the refrigerating system is lowered.